1. Field of the Invention
The present invention relates to a roller bearing equipped with a roller retainer, such as a needle roller bearing, which can be employed in an application similar to that in which the full complement roller bearing having an outer race is employed, and also relates to a method of assembling such roller bearing.
2. Description of the Prior Art
In the application where the outer diameter of the bearing is limited and, on the other hand, a relatively large load bearing capacity is required, the full complement roller bearings have hitherto been employed in general. Since the full complement roller bearing has no pillar intervening between the neighboring rollers, the number of rollers employed therein can be increased as compared with the retainer-equipped roller bearing and the load bearing capacity can therefore be increased.
However, since the full complement roller bearing makes no use of the roller retainer, it is often experienced that some or all of the rollers tend to separate or fall from the right position during the handling thereof prior to the full complement roller bearing being installed on a machine or equipment. For this reason, various suggestions have hitherto been made to achieve a non-detachability of the rollers, that is, to enable the roller to be retained in position. For example, the Japanese Laid-open Patent Publication No. 6-307456 discloses rollers each having its opposite end faces steepled coaxially outwardly so that a press-worked outer race having collars formed at its opposite ends can saddle each roller with the collars receiving the steeples of the respective roller. The Japanese laid-open Patent Publication No. 7-238940, for example, discloses the filling of a thermally curable grease to achieve the non-detachability of rollers in the full complement roller bearing.
The first full complement roller bearing employing the rollers formed with the steeples has the following problems:
The effective length of each roller tends to be reduced a quantity corresponding to the size of the steeples formed therein.
Since the opposite end faces of each roller are steepled or have the steeples, the frictional wear of the roller end faces tends to be prominent when the full complement roller bearing is employed in the environment where an induced thrust force is large.
Since the opposite end faces of each roller are steepled or have the steeples, the roller is costly as compared with the roller having flat end faces.
On the other hand, the second full roller bearing utilizing the thermally curable grease has the following problems:
The use of the thermally curable grease limits the temperature under which the full complement roller bearing can be operated.
The type of grease and the type of oil are limited.
In view of the foregoing, it has been suggested in, for example, the Japanese Patent Application No. 2003-285566 that in the retainer-equipped roller bearing a generally ring-shaped roller retainer having a plurality of pockets defined spacedly in a direction circumferentially thereof is made of a synthetic resin deformable in a direction radially thereof and, on the other hand, a pillar present between the neighboring pockets retains the respective roller from a radially inner side of the roller bearing and has an outer diameter smaller than the diameter of the pitch circle in which the rollers are arranged.
According to the suggested design, the rollers can be retained in the respective pockets of the roller retainer by, after the rollers have been mounted around an inner periphery of the outer race, inserting the roller retainer into the circular row of the rollers while deforming a portion of the roller retainer radially against its own elasticity and by subsequently allowing the roller retainer to restore to the original shape or diameter.
However, even the full complement roller bearing of the suggested design has the following problems:
Since the assemblage requires a portion of the roller retainer to be radially deformed against its own elasticity, utmost care is required to avoid an undesirable reduction in shape precision of the roller retainer after the assemblage, which would otherwise occur as a result of the deformation.
Since during the assemblage that portion of the roller retainer is radially deformed against its own elasticity, automation of the assembly line is difficult to achieve.